Portable electronic products, such as cellphones and wearable electronic devices are in increasingly wide uses. However, power losses may increase as such portable electronic products have more functionality. Therefore, the service time of portable electronic products may be limited by the battery level, so as to cause adverse effects on user experience. A movable power source is a portable charger with both power supply and charging functions such a movable power source can be used to charge a portable electronic product whenever and wherever possible, or to supply power in a standby state, in order to prolong service time. Movable power source typically include a power supply circuit and an additional battery, such as a lithium battery.